Electric multistep controller



Jan. 11,1944. w, RAYMOND 2,339,191

' EDECTRIC I MULTISTEP CONTROLLER Filed Feb. 8. 1939 4 Sheets-Sheet 1INVENTOR I Wan/Rqymmd Jib. 11, 1944. w. RAYMOND- 1 2,339,191

ELECTRI C MULTI S TEP CONTROLLER Filed Feb. 8, 1939 4 Sheets-Sheet 2 I 71 I 1\ Z a. k g; =E

l1) INVENTOR J n. 1 1, 1944- w. RAYMOND 2,339,191

' ELECTRIC MULTISTEP CONTROLLER Filed Feb. 8, 1939 4 Sheets-Sheet 3 &

INVENTOR l m Ra mand ATTORNEY Jan. 11, 1944.

ELECTRIC MULTISTEP CONTROLLER Filed Feb. 8, 1939 4 Sheets-Sheet 4ATTORNEY w. RAYMOND 4 2,339,191

I Patented Jan. 11, 1944 ELECTRIC MULTISTEP CONTROLLER Ward Raymond,Easton, Pa., assignor to The Pennsylvania Pump & Compressor Company,Easton, Pa., a corporation of Pennsylvania Application February 8, 1939,Serial No. 255,194

Claims.

This invention relates to compressors and has for its primary object anovel and efiicient means for unloading or controlling the output of anair or gas compressor so that the amount of air or gas delivered by thecompressor may be varied to suit an intermittent or irregular demand.

Several different systems have been employed heretofore to obtain thisresult. In some cases the intake is closed and opened intermittently, orthrottled to reduce the inflow. In other cases the inlet valves are heldopen, allowing the air drawn into the cylinder on the suction stroke tobe discharged back into the suction instead of being compressed. Anothermethodis to employ additional valve controlled clearance spaces orpockets communicating with a cylinder which may becut in or out to varythe efiective clearance volume and thereby control the amount of air orga compressed.

Substantially all these plans, with the exception of throttling, whichis not economical, operate in steps of comparatively large magnitude,and when the demand falls between two consecutive steps, one of thesteps must be cut in and out repeatedly to meet the intermediate demand.

Still another method of control is by holding the inlet valves open foronly a portion of the compression stroke, during which portion of thestroke air in the cylinder is expelled through the inlet valves. Afterallowing the valves to close at a point in the compression stroke, theair remaining in the cylinder after the valve closes is compressed. I amaware that this has been done, but my present invention proposes tocontrol the output of air or gas compressors by the employment ofelectric devices including magnets energized for longer or horterperiods during the stroke of the piston, whereby the inlet valves areheld in their open position during such portion of the compressionstroke as will cause the compressor to deliver substantially the amountof air demanded of it at the moment,'and to vary the period during whichthe valve is held open as the demand may vary.

Briefly, my invention employs suitable electric magnets Or otherelectrically controlled means operating in conjunction with one or moreof the inlet valves of the cylinder or cylinders, whereby theinletvalves may be held open during such period of each compressionstroke of the piston as is necessary to properly reduce the output ofthe compressor, and then allow it to close and the air remaining in thecylinder to be compressed and discharged in the usual manner.

Thi electric control is obtained by means of a timer or distributeroperated in synchronism with the compressor crank shaft, and in whichthe portion of the compression stroke of the piston during which thevalve is open is varied by means under the control of the dischargepressure of the air or gas being compressed.

In the drawings and description I have shown my invention as applied toan air compressor of the duplex horizontal two-stage cross-compoundtype, but it will be understood that the invention is not limited tocompressors of this type, as my invention may be incorporated in otherstandard types, it only being required that the compressor has one ormore compressing cylinders of the reciprocating piston type and hasinlet valves normally open during the suction and closed during thecompression stroke. In its simplest form the invention would be appliedto a compressor having one compressing cylinder and of the single ordouble-acting type.

While I herein describe my invention as applied to an air compressor, itwill be understood that it is equally suitable for other gases, and Ihave used the term air in orderto facilitate the description.

Referring to the drawings, Fig. 1 shows in plan a duplex two stage crosscompound air or gas compressor of one of the types for which myinvention is suitable,

Fig. 2 shows a side elevation of the compressor shown in Fig. 1;

Fig. 3 shows an end View of the compressor shown in Figs. 1 and 2 withthe compressing cylinders in section and showing the valves andoperating devices therefor. Fig. 3a is a detail sectional view of anintake valve and the means for holding it open;

Fig. 4 shows the timing or distributing mechanism for the valve openingmeans.

7 Fig. 5 shows a. detailed view of certain parts of the timer shown inFi 4. upon an enlarged scale: Fig. 6 shows diagrammatically-the wiringof a suitable electric circuit; and

Fig. 7 shows an alternate mechanism for oper ating the valves.

cooler 6. All of the foregoing parts are or may be of the usual orstandard type and will not require further description.

In Fig. 3 are shown the low pressure inlet valves 1 and discharge valves8, as well as the high pressure inlet valves 9 and discharge valves IDat one end of the cylinders. These valves, being of the usual disc, ringor leaf type, will not require further description. It will beunderstood that there are similar valves at the opposite ends of thecylinders.

As previously explained, the method of unloading this compressorconsists in holding the inlet valves 1 and 9 off their seats for a.greater or less portion of the compression stroke of the piston orpistons, and I will now describe one form of means for doing this. Asthe same description applies to both low and high pressure'cylindervalves, the same descriptive numbers will be used a for both.

Beneath the valve discs I I are hubs 12 carrying lifting fingers l3which enter the intake ports, and when'moved into contact with the valvediscs ll force these discs off their seats and thereby hold them open.On the discharge stroke of the piston therefor theair or gas will not becompressed while the inlet valve is open but will be free to return intothe intake. Engaging these hubs [2 are the stems M. The stems l4 passout through the covers l5,in fact, pass through a central bore in thesetscrews l6 which retain the valve asesmblies in position. Whennecessary to retain pressure, or when gas is compressed, suitablepackings I! may be provided to prevent leakage through the bore insetscrew It. At the outer end of each stem I4 ismounted a case [9containing an electric magnet 20 shown in conventional form only. Thesemagnets may be en'- closed by the covers 2|. Cases l9 and covers 21 forma complete unit of the proper materials and designto aid in theenergizing and rapid deenergizing of the magnets 20, and there is a unitprovided for each inlet valve.

The magnets 20 are energized through the connections 22A and 22B in acircuit presently to be described. It will now be seen from the abovedescription that upon the energizing of magnets 20 theirrarmatures l8will be drawn toward them. This movement of the armatures, actingthrough stems I4 and lifting fingers I3, will move the valve discs I Iaway from their seats and thereby hold the valves open.

Upon opening the circuit including connections 22a and22b andde-energizing a magnet 20 controlled thereby its armature I8 will bereleased through the action of spring I2A and the valve will be allowedto close.

As the magnets 20 operate individually on the inlet valves to hold themopen, it will be apparent that if the inlet valves at one end of acylinder were held open during the whole of the compressing stroke, allthe air in the cylinder would be forced back through the inlet valvesand no air would be compressed during that stroke. On the other hand, ifthe magnets 20 were de-energized at the middle of the stroke and thevalves allowed to close at that point, the air remaining in the cylinder.(half a cylinder full), would be compressed and forced through thedischarge valves in the usual way. 'At whatever portion of the strokethe inlet valves at one end of a cylinder are released and close, theremaining portion of the full capacity of the compressor will bedelivered.

Referring now to Figs. 4 and 5, Fig. 4. shows a distributor suitable foroperating the inlet valves in the manner described. On the base 23 ismounted the shaft 24 driven in synchronism with the compresssor mainshaft 2 by the sprocket 25 and chain 25A. The shaft 24, if desired, maybe driven by the synchronous motor 26 electrically locked in step withthe main shaft 2 when driven by a synchronous motor. It is only requiredthat the shaft 24 revolve in uniformity and fixed angularity of rotationwith shaft 2. On each shaft 24 is a drum 2'! keyed thereon by key 28 butfree to slide longitudinally thereon. The position of drum 2! on theshaft 24 is determined by a bell crank 29 pivoted in the bearing 30 inthe base 23 and having pins on the vertical arm engaging an annulargroove at one end of the drum 2?. Controlling the longitudinal movementof drum 21 through hell crank 29 is the pressure cylinder 3| with thepiston 32 and stem 33 bearing against the bell crank 29.

Air discharged from the compressor system is supplied through connection34 to force the piston 32 upward, and this is balanced by the weights 35on the horizontal arm of bell crank 29. These weights are adjusted tobalance the air pressure required in the system. The piston 32 may beprovided with a lower flange 36 which is submerged in oil or other fluidto act as a dashpot and dampen any suddent movement of the pis-' ton 32.The angular movement of the bell crank 29 may be limited, by anysuitable means not shown.

It will now b apparent that any change in discharge pressure of thecompressor system will cause movement of piston 32, and this pressureacting through bell crank 29 will cause a longitudinal movement of drum2'! along shaft .24. In order that a slight change in air pressure willnot cause a complete movement of piston 32 and drum 2?, I may providethe spring 31 fulcrumed against one arm of the bell crank 29 adJacentthe joint 39, so that the upward movement of .piston 32 will be opposedby the increasing resistance of spring 31, and a position of stabilitymaintained at a point in its movement according to the dischargepressure. The dampening eifect of this spring may be varied in two ways,first, by changing the compression of the spring tln'ough nut 39, sothat the total loading of the bell crank 29 may be varied, and second,by changing the position of the fulcrum 40 (n the bell crank 29 so thatthe amount of movement for a given increment of pressure change may bevaried.

On the drum 21 is acam 4! having its surface raised above the surface ofthe drum, as is clearly shownv in Fig. 5. One edge of this cam isstraight and lies parallel to the axis of the drum. The other edge isinclined or helical, wrapping itself a portion of the way around thedrum, all as will later be explained.

Surrounding the drum 2! is the mounting block 42, preferably made of aninsulating material such as fibre. This block may be mounted in fixedposition upon suitable supports 43. On this mounting block 42 aremounted a series of distributing members, one for each set of valves tobe controlled, four being shown in this figure, one member for theinlet'valves at each end of each cylinder.

For convenience, I have shown these distributing elements of the typecommonly employed in the ignition system of an automobile, as this issimple and readily understood, but I do not limit myself to thisparticular construction, .as others.

for instance a wiping contact on the cam surface 4| acting as oneterminal might be substituted. As these four distributers are alike, butone will require description.

On a stud 44 outstanding from the block 42 is hinged an arm 45 carryingthe cam block 46 adapted to ride upon the surface of the drum 21. Thisblock may preferably be of fibre or similar material. Mounted on the arm45 is the spring 45a, the outer end of which is secured in the post 41.The spring is secured to the arm as by rivets 48, leaving a free endthereof to which is secured the contact point 49 passing through anopening in arm 45 as shown. Mounted above this contact member andadjustable in the support 50 is the adjustable contact point 5|.

It will now be seen that as the drum 21 revolves and as long as the camblocks 46 ride upon the surface of the drum 21, the circuit betweencontacts 49 and 5| will be open, but during rotation of the drum whenthe cam 4| member comes beneath a block 46, it will be lifted. and withproper adjustment of contact 5| the circuit will be closed. The contact49, being mounted on the free end of spring 45, provides a firm closingof the contacts, regardless of slight irregularities in the movement ofthe arm 45. This is shown in the case of the one cam block in contactwith the cam.

The function of these four distributing elements is to supply current tothe circuits for the electric magnets and to energize and de-energizethem in the proper order and at the proper time during the stroke of thepistons.

These four distributing elements are therefore wired in electricalconnection with the magnets on the four sets of inlet valves in theorder marked. That is, the distributer marked 22B- LPI-IE is wired inconnection with the magnets on the inlet valves in the head end of thelow pressure cylinder, the distributer marked ZZB-LPCE is wired to themagnets in the crank end or the low pressure cylinder. The other twodistributers are similarly wired to the valves in the ends of the highpressure cylinder.

The wiring circuits are completed as shown in Fig. 6 by connecting theseveral terminals 4! by connections 22C to one common lead, and theterminals 22A from the magnets 25 to another common lead, these two'inturn being connected to a suitable source of current.

Referring again toFigs. 4 and 5 showing the distributing mechanism forthe cross compound compressor selected for illustration, it will be seenthat the four distributers are spaced equally around the drum 21, thosefor the opposite ends of each cylinder being on the opposite sides andthe others at 90 degrees to them. Therefore, the action of anydistributer upon the valves it controls will be duplicated by the otherdistributers on the valves they control.

To explain the operation, we will assum the drum 21 to be-in about theposition shown in Figs. 4 and 5. In this position that portion of thecam 4| directly beneath the cam blocks extends approximately 90 degreesaround the drum 21, or one quarter of the revolution. Now, with the drumso placed that slightly before the end of the suction stroke on the headend of the low pressure cylinder, the leading edge or cam 4| passesbeneath the cam block 45 for that distributer, the arm 45 will belifted, closing the contacts 49 and 5|. This in turn energizes themagnets 20 on that end of the cylinder, bringing the drum 2'! in theposition-shown in Fig. 4) the.

trailing edge of the cam 4| passes from beneath the com block 45,opening thecontacts 49 and 5|. 7

The opening of this circuit immediately de-energizes the magnets 24controlled thereby allowing the solenoid H? to release and permit spring|2a to move the hub I2 and valve engaging fingers l3 away from thevalves. The valves being new free close and the air remaining in thecylinder is V compressed and discharged in the usual manner; In likemanner the cam 4| as it rotates will con-' trol in the proper order theother sets of Valves in the other ends of the cylinders.

In theillustration above we assumed the com pressor operating at abouthalf capacity. We will now assume the compressor starting up from rest,or with little or no pressure in the system. In such a case, the airpiston 32 in cylinder 3| would be at its lowest point and the drum 2?atits extreme position to the right. In this position the narrowestportion of cam 4| passes beneath the cam blocks 45, reducing to aminimum the time during which the valves are held open, or the drum 2?may be arranged to pass suificiently far to the right for the end of thecam 4| to pass beyond the line of the cam blocks. In that case themagnets would not be energized at all, and the inlet valves would befree to function in their usual manner delivering the full capacity ofthe compressor.

As the pressur in the system rises to that at which the controlfunctions, the piston 32 rises, moving the drum 2! to the left as seenin Fig. 4. At first, as the narrow end of the cam 4| engages the camblocks 46, the magnet will be energized but a short time, simply holdingthe valves open while the piston-is passing through the end of thestroke and then allowing them to close. In this condition the compressorwill be delivering substantially its full capacity.

As the pressure continues to rise, the drum 21 will be removed furtherto the left. This will cause wider and wider portions of the cam 4| topass beneath the cam blocks 46, thereby lengthening the period duringwhich the magnets 20 are energized and the inlet valves held open.Finally, as the maximum pressure is reached and the drum is at theextreme left where the cam 4| extends half way around the drum, thevalves will be held open during substantially the entire compressionstroke and no air will be compressed. The extreme right hand end of thecam 4| may be extended entirely around th drum so that when the drum isin its extreme left hand position the contacts 49 and 5| will be keptcontinuously closed and the valves held continuously open.

The regulation of the compressor output is not, therefore, in steps orincrements of appreciable amounts, but consists of the gradual reductionor increas at all times determined or measured by the particular demandfor air at the time as indicated by a slight rise or fall of dischargepressure in the system.

In Fig. 4 I have'for convenience shown the element controlling themovement and position of drum 2! as an air cylinder under the influenceof the discharge pressure of the air in the system and operating throughthe bell crank 29, but it is obvious that any equivalent demandcontrolled motor may be employed.

It may happen at times that for some reason, as for instance, the sizeof the inlet valves, that they can not be readily operated directly bymagnets. In Fig. '7 I have shown an alternate method for moving thevalve holding member l2 whereby a small electrically controlled valvesupplies air for the motive power. In Fig. 7 the magnet case I9 isreplaced by the cylinder 52 containing the power piston 53. In closeproximity to this cylinder is an electrically controlled air valve 54,preferably of the solenoid type, having th air inlet 55, outl t 56 andexhaust 51. The outlet 55 is connected to cylinder 52.

When the circuit 22A.22B is energized, the solenoid within casing 58will open the air valve and supply air under pressure to piston 52 tooperate the valves H, as before described. Upon opening the circuit, theair in cylinder 52 will be exhausted through exhaust 51 and the valve IIwill b released.

In the foregoing description, four distributing elements are shown asrequired for a two-cylinder, double-acting compressor, but it is obviousthat for a double-acting, single cylinder but two elements would berequired, and for a single cylinder compressing in one direction onlyone element would be necessary. In the case of a compressor with morecylinders, the corresponding increased number of elements would berequired.

I claim:

1. A regulator for compressors comprising in combination, a cylinderhaving a piston movable therein and inlet and discharge valves at theopposite ends thereof, members movable to positions to render one ofsaid sets of valves inoperative, electro-magnetic means controlling saidmembers, and a distributer operating in synchronism with said compressorto alternately energize and de-energize said electro-magnetic means, acam on said distributer, and pressure operated means to vary theposition of said cam to vary the period said electro-magnetic means areenergized and said valve held inoperative during the stroke of thepiston.

4 ble width, and pressure operated means to vary the position of saidcam to vary the period said electro-magnetic means are energized andsaid valves held inoperative during the stroke of the piston.

3. A regulator for compressors comprising in combination, a cylinderhaving a piston movable therein and inlet and discharge valves at theopposite end thereof, member movable to positions to render the inletvalves inoperative at each end of said cylinder, electro-magnetic meanscontrolling said members, a rotating distributer operating insynchronism with said compressor and having contactsadapted to be openedand closed in circuits for said electro-magnetic means, a cam on saiddistributer having a variable width, and pressure operated means to varythe portion of said cam efiective to close said contacts and vary thetime said valves are held open during the stroke of the piston.

l. A compressor regulator comprising in combination, a cam rotated intimed relation with the compressor, pressure actuated means to move saidcam axially, electric circuits having contacts opened and closed byrotation of said cam, electro-magnets energized when said contacts areclosed, and unloading means operated by said electro-magnets.

5. A compressor regulator comprising in combination, a cam rotated intimed relation with the compressor, said cam having a raised portion ofgradually increasing width extending axially along its cylindricalsurface, pressure actuated means to move said cam axially, electriccircuits having contacts opened and closed by rotation of said cam,electro-magnets energized when said contacts are closed, and unloadingmeans operated by said electro-magnets.

WARD RAYMOND.

